As an effective and minimally invasive treatment, brachytherapy (radioactive particle implantation) for prostate cancer has become more and more widespread in China in recent years. Our hospital has been carrying out this treatment for more than 10 years, and is the earlier unit in China to carry out particle implantation, and has accumulated more experience. The following is a brief introduction.
1. Overview
Brachytherapy includes intracavitary irradiation and intertissue irradiation, which is a sealed radiation source placed directly into the natural cavity of the body or into the tissue being treated. Prostate cancer brachytherapy includes brief insertion therapy and permanent particle implantation therapy. The latter, also known as inter-tissue implantation of radioactive particles, is more commonly used and is aimed at increasing the local dose to the prostate and decreasing the radiation dose to the rectum and bladder through accurate positioning of the radioactive particles in the prostate gland with a three-dimensional treatment planning system. Permanent particle implantation therapy is commonly used with 125 iodine (125I) and 103 palladium (103Pd) with half-lives of 60 days and 17 days, respectively. Short-term implantation therapy is commonly used with 192 iridium (192Ir).
2.Indications
The American Brachytherapy Society (ABS) criteria are recommended.
(1) The following three conditions are also met as indications for brachytherapy alone.
(1) Clinical stage T1 to T2a.
(ii) Gleason classification of 2 to 6.
(3) PSA <10ng/ml.
(2) Indications for brachytherapy combined with external radiotherapy if any of the following conditions are met.
(i) Clinical stage of T2b and T2c.
(ii) Gleason grade 8 to 10.
③PSA > 20ng/ml.
④peripheral nerve invasion.
⑤ Positive pathological findings on multi-point biopsy.
⑥positive pathological results of bilateral biopsies.
(⑦) MRI examination clearly shows extra-prostatic envelope invasion.
Most scholars recommend external radiotherapy followed by brachytherapy to reduce the complications of radiotherapy.
(3) If the Gleason score is 7 or PSA is 10-20 ng/ml, the combination of external radiotherapy should be decided on a case-by-case basis.
(4) Indications for brachytherapy (or combined external radiotherapy) combined with endocrine therapy: prostate volume > 60ml, neoadjuvant endocrine therapy can be performed to shrink the prostate.
3. Contraindications.
(1) Absolute contraindications.
(1) Expected survival of less than 5 years.
(ii) Large post-TURP defect or poor prognosis.
(iii) Poor general condition.
④Distant metastasis.
(2) Relative contraindications.
①Gland greater than 60 ml.
(ii) previous history of TURP.
(iii) Prominent middle lobe.
④severe diabetes mellitus.
⑤ history of multiple pelvic radiotherapy and surgery.
Each patient should undergo a dosimetric evaluation after particle implantation, usually with CT. A premature CT examination after implantation may show an increase in prostate volume due to prostate edema and bleeding, and the dose assessment made at this time may underestimate the dose to the prostate. Therefore, it is recommended that a dose assessment 4 weeks after implantation is most appropriate. If a low dose area is found, additional reimplantation of the particles should be done promptly; if a large low dose area is found, external radiotherapy can be considered.
4.Technique and standard
For patients treated with brachytherapy alone, the prescribed dose is 144Gy for 125I and 115-120Gy for 103Pd; for combined external radiotherapy, the dose of external radiotherapy is 40-50Gy, while the doses of 125I and 103Pd are adjusted to 100-110Gy and 80-90Gy, respectively.
All patients treated with particle implants should be planned before implantation, and the expected dose distribution should be given according to the 3D treatment planning system. The prostate volume is usually determined using transrectal ultrasound (TRUS) first, and then the treatment plan is developed based on the prostate contour and cross-section depicted by TRUS, including the location of the implant needle and the number and activity of the particles. Intraoperatively, TRUS should be used again for planning and placing the particles according to the dose distribution profile. Transrectal real-time ultrasound should also be used to guide the operation during the particle implantation process and to adjust the change in dose distribution due to the deviation of the implantation needle at any time. It should be noted that the area covered by the prescribed dose in the prostate target area should include the prostate and its surrounding area of 3 to 8 mm. Thus the prostate target area is approximately 1.75 times the actual prostate volume.
5. Complications
Complications include short-term complications and long-term complications. Complications that occur within 1 year are usually defined as short-term complications, while complications that occur after 1 year are defined as long-term complications. These complications mainly involve the urinary tract, rectum and sexual function.
Short-term complications: urinary tract irritation such as frequent, urgent and painful urination, difficulty in urination and increased nocturia. Short-term complications include urinary tract irritation such as increased frequency and urgency, rectal irritation, proctitis (mild blood in the stool, intestinal ulcers and even prostatic fistula), etc.
Chronic urinary retention, urethral stricture, and urinary incontinence are common long-term complications.
In conclusion, brachytherapy for prostate cancer is another promising method to cure limited prostate cancer after radical prostatectomy and external radiotherapy, which is efficacious and less invasive, especially suitable for elderly prostate cancer patients who cannot tolerate radical prostatectomy.